Liquid cooled rotor and stator



United States Patent 3,007,064 LIQUID COOLED ROTOR AND STATOR Elmer F. Ward, Orange, Calif'., assignor to The Task Corporation, Anaheim, Calif., a corporation of California Filed Apr. 4, 1958, Ser. No. 726,415 Claims. (Cl. 310-54) This invention relates generally to liquid cooled electrical machinery, and more particularly has to do with liquid cooling of electrical motors, particularly induction motors at least partially surrounded by liquid coolant and driving mechanism operable to froth the coolant prior to circulation thereof through the motor.

Motors designed to drive mechanism bathed in a lubricant that is also taken into the motor for cooling purposes are subject to overheating due to improper cooling when the coolant does not flow through the motor in a continuous stream. One not uncommonly encountered circumstance causing discontinuous fiowage of the coolant through a motor is the presence of extensive froth or bubbles dispersed in the circulating coolant. Formation of such froth may often be traced to the churning action of gear mechanism driven by the motor shaft While submerged in the coolant-lubricant outside the motor housing.

The present invention has for its major objects the provision of an improved liquid cooled electrical motor and also the correction of this problem source of overheating of electrical motors, and is predicated on the concept of physically collapsing the coolant froth before it is circulated through rotor and stator passages in the motor assembly. Accordingly, there is incorporated in the motor assembly an axial flow type rotary impeller positioned in the path of coolant circulation prior to entrance thereof into the rotor and stator passages, so that coolant froth upon passage through the impeller is collapsed and a steady pressurized stream of coolant-lubricant is delivered to the cooling passages in the motor assembly. The invention particularly contemplates the provision of a spiral vane type impeller delivering coolant to rotor passages, the froth eliminating impeller operating in conjunction with a centrifugal impeller located downstream from the rotor passages for throwing the de-frothed coolant radially outwardly toward stator passages, from which the coolant exits from the motor to the exterior bath.

Additional objects include particularly advantageous structural incorporation of the impellers in the motor assembly to achieve the results desired.

These and other features and objects of the invention, as well as the details of an illustrative embodiment, will be more fully understood from the following detailed description of the drawings, in which:

FIG. 1 is an elevation taken in section through the electrical motor and the impellers incorporated therein;

FIG. 2 is a section taken on line 2-2 of FIG. 1; and

FIG. 3 is a view similar to'FIG. 1 showing a modified motor and impeller assembly.

In FIG. 1 the motor housing generally indicated at 10 includes a receptacle 11 having a flange 12 extending about the receptacle, and a cap 13 closing the open end of the receptacle, the cap and receptacle having aligning engagement at 14. Extending axially within the motor housing 10 is a rotor shaft 15 journaled in bearings 16 and 17 respectively carried by a receptacle boss 18 and "ice by the cap portion 19, the shaft projecting through the cap to the exterior. The rotor drives gear mechanism 20 including a spur gear 21 mounted on the threaded end of the motor shaft and other gearing generally indicated at 22. It will be understood that the gear mechanism and that portion of the motor housing leftward of the flange 12 are bathed in a lubricant-coolant, such as a light oil lubricating the gearing and being taken into the motor housing for cooling purposes.

Carried by the rotor shaft 15 intermediate the bearings 16 and 17 is a laminated iron core 23, the laminations of which extend in planes perpendicular to the shaft axis. A series of circularly spaced, axially directed parallel conductor bars 24 are received or sunk in the core, forming the common squirrel cage associated with induction motors. These bars are shorted at their opposite ends by conductor rings 25 and 26 typically made of copper, as are the bars. The iron core laminations 23 form three axially extending passages 27 spaced about the rotor shaft for conducting coolant axially through the rotor assembly.

The coolant is received from the exterior of the housing through a series of circularly spaced inlets 28 in the cap for delivery to the passages 27 by an axial flow type impeller 29. The latter includes a spiral vane 30 carried by a sleeve 31 on the rotor shaft, with a ring shaped partition 32 integral with the cap closely surrounding the periphery of the spiral vane so as to form in effect a pump casing. From the impeller the coolant enters passages 27 through a reduced opening 33 formed by the conductor ring 25, the latter together with the partition 32 effectively sealing off the impeller chamber 34 and the entrance ends of passages 27 from the stator passages to be described, the annular seal being eifected at 35.

After passing axially through passages 27, the coolant enters the eye 36 of a centrifugal impeller, the eye being formed by conductor ring 26. The centrifugal impeller is also mounted on the rotor shaft so as to operate in conjunction with the defrothing impeller 29 upstream of the entrance ends of passages 27. Coolant passing through the centrifugal impeller is thrown radially outwardly toward the stator passages to be described. The stator includes an elongated laminar core 38 containing openings, not shown, through which the stator windings extend in an axial direction, the windings at opposite ends of the core, as shown by Winding rings 39 and 40, being cooled by the flow of coolant as indicated by the arrows. Ring 39 extends generally in the annular space 41 formed at the closed end of the motor between boss 18 and the receptacle outer wall 42, the winding ring being displaced radially outwardly from the impeller 37. Winding ring 40, on the other hand, extends in the annular space 43 formed between the partition 32 and the outer wall 44 of the cap.

' The stator is held in position in the housing by a set screw 45 threaded into the cap wall and received in the stator core. Endwise extending annular passages are formed between the housing wall and the stator core 38 as designated at 46, and also between the stator core and the rotor conductor bars 24, as designated by the gap 47 therebetween. The coolant delivered by the centrifugal impeller is free to flow axially through passages 46 and 47 from space 41 to space 43, in cooling relation with the stator, the coolant exiting from. the motor via outlet 48 in the cap. As described previously, the seal at 35 3 prevents short-circuiting of coolant from the impeller chamber 34 directly into the space 43.

In operation, the spiral vane 30 rotated by shaft 15 collapses the froth and bubbles formed in the coolant by the gearing 30, so that a steady defrothed stream of coolant is delivered through the rotor passages 27 to the centrifugal impeller 37. The latter operates to deliver the steady stream of coolant under pressure to the endwisc extending stator passages 46 and 47. Coolant in spaces 34 and 41 is, of course, free to lubricate the bearings 16 and 17 exposed to those spaces.

Referring now to FIG. 3 a somewhat modified form of the invention is illustrated. A motor housing receptacle 50 and end cap 51 receive the rotor shaft 52 journaled in bearings 53 and 54, similar to those previously described, the shaft projecting through the cap at 55. The latter takes coolant in through side inlets 56 to an annular chamber 57 formed between the shaft and wall 58 of the cap. The spiral vane impeller 50 in the space 57 defroths the coolant and delivers same through radial openings 60 in the rotor shaft to an axially extending passage 61 in the shaft. In this embodiment, the coolant flows axially through the passage 61 toward bearing 54 in cooling relation with the rotor shaft, and exits through a number of radial openings 62 in the shaft into the centrifugal impeller 63 mounted on the shaft. From there, the coolant flows as previously described through the stator passages 46 and 47, and finally exits through outlets 65 in the cap, after flowing in space 66. An annular seal ring 67 mounted against shoulder 68 on the rotor shaft extends to the inner wall 69 of the cap and seals off between space 57 and 66, to prevent short-circuiting of the coolant around the rotor and stator passages.

In flowing through the shaft passage 61, the coolant absorbs heat generated in the annular rotor core laminations 70 and transferred to the rotor shaft by conduction, the laminations being mounted directly on the shaft and containing no passages as were indicated at 27 in FIG. 2.

I claim:

1. A liquid cooled electrical machine, comprising means including a housing and rotor and stator assemblies within the housing, said means containing an inlet and an outlet and passages for circulating a coolant received through said inlet along said rotor and stator assemblies to discharge from said outlet, said coolant circulation passages including gaps between the rotor and stator and between the stator and housing, said rotor assembly including a shaft projecting outside the housing for driving mechanism operable to froth the coolant prior to circulation thereof through said inlet, and a rotary impeller in the path of said circulation for delivering received coolant to said passages in response to rotor assembly rotation, whereby coolant froth received through said inlet is collapsed by said impeller prior to coolant circulation through said passages.

2. A liquid cooled electrical motor, comprising means including a housing and coaxial rotor and stator assemblies within the housing, said means containing an inlet and an outlet respectively communicating with the rotor and stator assemblies and axially directed rotor and stator passages in series communication for circulating a coolant received through said inlet successively along said rotor and stator assemblies to discharge from said outlet, said rotor assembly including a shaft projecting outside the housing for driving mechanism operable to froth the coolant prior to circulation thereof through said inlet, an axial flow type rotary impeller in the path of said circulation for delivering received coolant to said passages in response to rotor assembly rotation whereby coolant froth received through said inlet is collapsed by said impeller prior to coolant circulation through said passages, and a second impeller downstream from said axial flow type impeller for delivering coolant received from said rotor passage to said stator passage.

3. The invention as defined in claim 2 wherein said impellers are axially spaced and rotatable by said rotor, said second impeller being of centrifugal type.

4. A liquid cooled electrical motor, comprising means including a housing and coaxial rotor and stator assemblies within the housing, said means containing an inlet and an outlet respectively communicating with the rotor and stator assemblies and axially directed rotor and stator passages in series communication for circulating a coolant received through said inlet successively along said rotor and stator assemblies to discharge from said outlet, said rotor assembly including a shaft projecting outside the housing for driving mechanism operable to froth the coolant prior to circulation thereof through said inlet, an axial flow type rotary impeller in the path of said circulation for delivering received coolant to said passages in response to rotor assembly rotation whereby coolant froth received through said inlet is collapsed by said impeller prior to coolant circulation, through said passages, and a second impeller downstream from said axial flow type impeller for delivering coolant received from said rotor passage to said stator passage, said impellers being axially spaced and rotatable by said rotor, said second impeller being of centrifugal type, said axial flow type impeller having a spiral vane facing the entrance to said rotor passage, and said stator passage extending along the outside of said stator assembly.

5. The invention as defined in claim 4 in which said rotor passage extends alongside the rotor shaft.

6. The invention as defined in claim 4 in which said rotor shaft contains said rotor passage.

7. The invention as defined in claim 5 comprising an induction motor in which said rotor assembly includes a plurality of circularly spaced and axially directed conductor bars and a conductor annulus connected with end portions of said bars, said annulus forming said entrance to said rotor passage.

8. The invention as defined in claim 7 in which said housing includes an annular partition cooperating with said conductor annulus to seal off between said rotor and stator passages.

9. A liquid cooled electrical motor, comprising means including a housing and coaxial rotor and stator assemblies extending lengthwise within the housing, said means containing an inlet and an outlet respectively communicating with the rotor and stator assemblies and axially directed passagesextending lengthwise along said assemblies and in series communication for circulating a liquid coolant received through said inlet successively lengthwise along said rotor assembly and then lengthwise along said stator assembly, said coolant circulation passages including gaps between the rotor and stator and between the stator and housing, said rotor assembly including a shaft projecting outside the housing for driving mechanism operable to froth the coolant prior to circulation thereof through said inlet, and a centrifugal impeller within the housing and rotatable by said rotor assembly in the path of coolant circulation for drawing said coolant through said rotor passage and for irnpelling said coolant outwardly toward said stator passage, and an axial flow type rotary impeller within the housing and rotatable by said rotor assembly in the path of coolant circulation upstream of said centrifugal impeller for collapsing coolant froth prior to coolant circulation through the major extent of said passages.

10. A liquid cooled electrical machine, comprising means including a housing and rotor and stator assemblies within the housing, said means containing an inlet and an outlet and passages for circulating a coolant received through said inlet along said rotor and stator assem-blies to discharge from said outlet, said coolant circulation passages including gaps between the rotor and stator and between the stator and housing, other means outside said passages for driving structure operable to froth the coolant prior to circulation thereof through 5 said inlet, and a rotary impeller in the path of said circulation for delivering received coolant to said passages in response to rotor assembly rotation, whereby coolant froth received through said inlet is collapsed by said impeller prior to coolant circulation through said passages. 10

References Cited in the file of this patent UNITED STATES PATENTS Arutunoff Mar. 31, 1925 Heintz Apr. 12, 1955 MOerk Feb. 14 1956 Philippovic Sept. 30, 1958 FOREIGN PATENTS Germany Mar. 21, 1941 

